In Broadcast - October 2015 - 78

www.inbroadcast.com | Vol: 5 - Issue 10 | October 2015

InAudio

Picking An ATSC 3.0 Audio Format
Is Cause For Sound Debate
As the standard debate rolls on, Contributing Editor Michael Grotticelli discusses the format
options that are being considered...

s the Advanced Television
Systems
Committee
(ATSC)
standards committee continues to
focus on developing the emerging 3.0
television broadcast specification for
the US into a full-fledged standard,
there appears to be some hot debate
about the 3D audio format that should
be included.
The
contenders
are
MPEG-H
(proposed by a pool of patent holders)
vs. AC-4 (developed by Dolby) and
the stakes are high for intellectual
property revenue. [A third proposal,
from DTS, was withdrawn by the
company earlier this year after it
lacked enough support within the ATSC
for its DTS:X audio system.]
Often referred to as "3D Audio,"
both new formats automatically adapt
audio program material to the target
number of loudspeakers in a given
consumer's listening venue. 3D Audio
supports the efficient transmission of
3D audio signals and flexible rendering
for the playback of 3D audio in a wide
variety of listening scenarios. These
include 3D home theatre setups,
loudspeaker systems, automotive
entertainment systems, and playback
over headphones connected to a tablet
or smartphone.
The MPEG-H Audio standard has
been in development for several years
and has many supporters. Prior to its
current round of testing within the
ATSC - and following a rigorous testing
and selection process that it said
included a ten test labs worldwide,
more than 50 listeners and more than

MPEG-H allows broadcasters to deliver
audio elements well beyond 5.1 surround
sound while incorporating new interactive
features that allow 3.0-compatible
television set viewers to customise their
audio experience

41,000 subjective responses - the
Moving Picture Experts Group (MPEG)
selected the Fraunhofer IIS channel/
object-based proposal to provide a
basis for the future MPEG-H 3D Audio
standard for the delivery of highquality 3D audio content.
Other developers involved with
MPEG-H include: Apple, DTS, ETRI,
Iosono, Philips, Qualcomm, Samsung,
Technicolor, Orange, and, yes, even
Dolby. It allows broadcasters to
deliver audio elements well beyond 5.1
surround sound while incorporating
new interactive features that allow
3.0-compatible television set viewers
to customise their audio experience in
new ways not possible before. Several
audio equipment manufacturers have
tested the format and have found
success with beta users. One vendor
in particular, Jünger Audio, has tested
a new multi-channel monitoring,
authoring and loudness processor for
the new MPEG-H 3D audio system,
which helps broadcasters maintain
compliance with loudness regulations
while avoiding the processing artifacts
of traditional loudness control
approaches.
Dolby's AC-4 is similar in that it
addresses the current and future
needs of next-generation video and
audio entertainment services that
include both terrestrial broadcast
television as well as Internet
streaming. The format is already
being implemented by a wide variety
of system-on-a-chip (SoC) designers,
consumer electronics manufacturers
and a variety of broadcast
equipment makers, such as
Arris, Ateme, Axon, DekTec,
Envivio, Ericsson, Harmonic,
Interra,
Linear
Acoustic,
Thomson, MStar, Sony, ST
Micro, TP Vision, and VIZIO,
to name a few. Dolby AC-4
is targeted for widespread
availability in consumer TVs
starting in 2017.
Both formats efficiently
deliver audio elements, alternate
language versions, and services
for hearing-impaired and visually
impaired audiences. Both also

Will consumers have to buy new compatible television sets and broadcasters new
encoders and transmission circuitry for their stations?

are based on object-based audio
capabilities, that is the ability to assign
individual sounds, or "objects' of a
scene to the space the viewers sitting
in. Rather than mixing for speakers,
the audio engineer is mixing for the
room.
This
capability
is
possible
with objects because the whole
representation of a sound includes
positional information in that room
(it's called "Cartesian coordinates").
This means future elite home theatres
will include added speakers on the
ceiling to "immerse" the viewer in
sound. This way every speaker in a
room can be targeted in a different
way. In fact, ATMOS, a cinema sound
system from Dolby, provides for up
to 128 discreet audio objects in any
one frame of video. There will also be
many variations of the technology,
such as 3D home theatre setups
that could include a single wireless
sound bar, professional theatre 22.2
loudspeaker systems, automotive
entertainment systems and playback
over headphones connected to a tablet
or smartphone, which all provide an
immersive experience.
With object-based audio codecs users
can also place individual audio objects
(or "elements") into specific speakers,
turn individual audio channels on and
off, change volume levels relative to
the other audio components, and, in
some cases, choose between alternate
channels, such as multiple announcer
streams and custom soundtracks. It's
all technically possible today (albeit in

highly controlled environments) and
has been demonstrated using different
methods.
So, why the debate, why not combine
the best attributes of the two? It
appears as though money is the
instigator here. Whatever format is
chosen as the official spec of the final
ATSC 3.0 standard, users of that spec
will have to pay a royalty fee.
While Dolby wouldn't comment
publically, privately it has provided
patent users with a royalty cost scale
that "is more cost-effective [than
MPEG-H]," said Dolby's Jeff Riedmiller,
because "you're buying a proven name
in the industry that stands behind its
products." There have been a series of
tests done in the US and in Europe with
local TV stations and manufacturers
to get the AC-4 standard on the
air, literally. A UHD TV broadcast
of the recent French Open Tennis
Tournament was compressed with
HEVC encoders supplied by Envivio,
alongside a Dolby-produced AC-4
audio signal; and Dolby also worked
with a Harmonic encoder to help San
Francisco, California-based Public
broadcast (PBS) TV station KQED-TV
become the US's first to broadcast a
live AC-4 signal on-air in July.
So one can see that for related
audio equipment manufacturers, as
well as broadcasters, the cost could
be significant - even if AC-4 appears
less expensive - whatever format is
chosen. Likewise, the windfall for
patent holders from IP royalties could
be huge.

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